Airworthiness Directives; General Electric Aircraft Engines CF34 Series Turbofan Engines

[Federal Register Volume 64, Number 206 (Tuesday, October 26, 1999)]
[Rules and Regulations]
[Pages 57556-57557]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-27788]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-62-AD; Amendment 39-11388; AD 99-22-10]
RIN 2120-AA64


Airworthiness Directives; General Electric Aircraft Engines CF34 
Series Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain General Electric Aircraft Engines CF34 series 
turbofan engines, that establishes new life limits for certain high 
pressure compressor (HPC) spools, stage 9 HPC disks, and rear HPC 
spools. This amendment is prompted by a cyclic life analysis using 
increased stress levels resulting from manufacturing discrepancies. The 
actions specified by this AD are intended to prevent HPC spool and disk 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft.

DATES: Effective December 27, 1999.

FOR FURTHER INFORMATION CONTACT: Eugene Triozzi, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7148, fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to General Electric Aircraft Engines 
(GEAE) Models CF34-1A, -3A, -3A1, and -3A2 turbofan engines was 
published in the Federal Register on April 5, 1999 (64 FR 16364). That 
action proposed to require removal from service of forward HPC spools, 
part number (P/N) 6078T56P01; rear HPC spools, P/N 6087T01P03 and 
6087T01P04; and stage 9 HPC disks, P/N 5087T46P01 or 5087T46P02. The 
affected parts must be removed prior to accumulating cycles in service 
beyond new, reduced cyclic life limits.

Comment Received

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comment received.
    The commenter supports the rule as proposed.
    After careful review of the available data, including the comment 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule as proposed.

Economic Analysis

    There are approximately 600 engines of the affected design in the 
worldwide fleet. The FAA estimates that 28 engines installed on 
aircraft of US registry will be affected by the requirement within this 
AD to replace the forward spool. The FAA has calculated the prorated 
cost for forward spool replacements to be $36,500 per engine, based on 
the estimated new part cost divided by the original life limit, 
multiplied by the number of cycles that will be reduced by the AD 
requirement. Therefore, the FAA estimates the total cost impact for 
replaced forward spools to be $1,022,000.
    The FAA estimates that 200 engines installed on aircraft of US 
registry will be affected by the requirement to replace the stage 9 
disk. The FAA has calculated the prorated cost for stage 9 disk 
replacements to be $3,500 per engine, based on the estimated new part 
cost divided by the original life limit, multiplied by the number of 
cycles that will be reduced by the AD requirement. The FAA estimates 
the total cost impact for replaced stage 9 disks to be $700,000.
    The FAA estimates that 300 engines installed on aircraft of US 
registry will be affected by the requirement to replace the rear spool. 
The FAA has calculated the prorated cost for rear spool replacements to 
be $8,900 per engine, based on the new part cost divided by the 
original life limit, multiplied by the number of cycles that will be 
reduced by the AD requirement. Therefore, the FAA estimates the total 
cost impact for replaced rear spools to be $2,670,000.
    The FAA has determined that it will take no additional work hours 
per engine to remove affected components, as removal would take place 
at available opportunities. Based on these figures, the total cost 
impact of the AD on US operators is estimated to be $4,392,000.

Regulatory Impact

    The regulations adopted herein will not have substantial direct 
effects on the

[[Page 57557]]

States, on the relationship between the national government and the 
States, or on the distribution of power and responsibilities among the 
various levels of government. Therefore, in accordance with Executive 
Order 12612, it is determined that this final rule does not have 
sufficient federalism implications to warrant the preparation of a 
Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a 
significant economic impact, positive or negative, on a substantial 
number of small entities under the criteria of the Regulatory 
Flexibility Act. A final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air Transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

99-22-10  General Electric Aircraft Engines: Amendment 39-11388. 
Docket 98-ANE-62-AD.

    Applicability: General Electric Aircraft Engines (GEAE) Models 
CF34-1A, -3A, -3A1, and -3A2 turbofan engines, installed on but not 
limited to Canadair aircraft models CL-600-2A12, -2B16, and -2B19.

    Note 1: This airworthiness directive (AD) applies to each engine 
identified in the preceding applicability provision, regardless of 
whether it has been modified, altered, or repaired in the area 
subject to the requirements of this AD. For engines that have been 
modified, altered, or repaired so that the performance of the 
requirements of this AD is affected, the owner/operator must request 
approval for an alternative method of compliance in accordance with 
paragraph (b) of this AD. The request should include an assessment 
of the effect of the modification, alteration, or repair on the 
unsafe condition addressed by this AD; and, if the unsafe condition 
has not been eliminated, the request should include specific 
proposed actions to address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent high pressure compressor (HPC) spool and disk 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft, accomplish the following:
    (a) Remove from service the following HPC spools and disks prior 
to accumulating cycles in service beyond new, reduced cyclic life 
limits, and replace with a serviceable part, as follows:
    (1) For forward HPC spools, part number (P/N) 6078T56P01, which 
have accumulated fewer than 6,000 cycles since new (CSN) on the 
effective date of this AD, remove prior to accumulating 6,000 CSN.
    (2) For forward HPC spools, P/N 6078T56P01, which have 
accumulated 6,000 or more CSN on the effective date of this AD, 
remove at the next shop visit after the effective date of this AD, 
but prior to accumulating 12,000 CSN.
    (3) For the purpose of this AD, engine shop visit is defined as 
engine disassembly that includes separation of the compressor 
section from the fan section front frame and from the combustion 
section combustion chamber frame.
    (4) For stage 9 HPC disks, P/N 6087T01P03 or 6087T01P04, remove 
prior to accumulating 20,000 CSN.
    (5) For rear HPC spools, P/N 5087T46P01 or 5087T46P02, remove 
prior to accumulating 17,000 CSN.
    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Engine Certification Office. 
Operators shall submit their requests through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, Engine Certification Office.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Engine Certification Office.

    (c) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the aircraft to a location where 
the requirements of this AD can be accomplished.
    (d) This amendment becomes effective on December 27, 1999.

    Issued in Burlington, Massachusetts, on October 18, 1999.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-27788 Filed 10-25-99; 8:45 am]
BILLING CODE 4910-13-P

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